This he
handed to Buck, who examined it casually as he bore it to the side of
the hole and handed it to the doctor.

"It's broken up granite, sir, for certain," he said, "and this other
side sparkles just like--"

He was going to say something, but the doctor excitedly, so to speak,
snatched the word from his lips.

"Yes," he cried--"gold!"

The two boys started forward excitedly.

CHAPTER THIRTY ONE.

AN EXPLOSION.

"Yes," said the doctor, as he scanned some little specks of the pale
yellow glistening metal, and the two blacks crept silently closer, "this
is gold, sure enough."

"I don't know much about these things," said Sir James, examining the
big flake carefully, "but I didn't think that it was possible to find
gold in cement. If it had been quartz rock, doctor--"

"Ah, you are thinking of gold ore, Sir James," said the doctor, taking
out his knife and opening it. "These are scraps of manufactured gold."

"Why, who could have manufactured them," said Mark sharply.

"We must go to history for that," replied the doctor, "and the only
people I can suggest would be the Phoenicians; but I may be quite wrong,
for gold has been searched for and used by most ancient people.--Allow
me, Sir James;" and he took back the piece of cement and with the point
of his knife picked out a little rivet, which he tried with a sharp
blade. "Yes," he said; "pure gold. You see it's quite soft. Why, I
can cut it almost as easily as a piece of lead. Here's another little
rivet. I should say this has been a piece cut off a length of gold
wire."

"But what would they want such little bits as that for?" asked Dean.

"For the purpose I name, as rivets, to fasten down gold plates. There
are more and more of them here--and look at this corner where the cement
has broken. Here's a scrap of thin hammered plate of gold. Why, boys,
we have come to the place where our little friend yonder must have
obtained his gold wire ornaments."

"But it isn't likely," said Mark, "that we should come by chance and dig
down in the right place."

"No, I don't think this can be the right place, but I do think that we
have come to the ruins where this precious metal is found."

"But that means," said Mark, now speaking excitedly, "that we have come
to a place where there must be quantities of such things."

"I think so too," said the doctor. "We have certainly made a very
curious discovery--one which may help us to find out who th